Field of the Invention
The invention relates to a circuit for load control of an internal combustion engine that takes in a mixture and has at least one electromechanically activated inlet valve. The invention also relates to a method for an emergency operation of the internal combustion engine. The load control of the internal combustion engine is performed exclusively by driving an activation device of the inlet valve.
Internal combustion engines whose charge cycle valves, in particular whose inlet valves, are activated electromechanically are known. In contrast to camshaft-activated valves, these valves are actuated so as to open and close as a function of the rotary position of the crankshaft; there is no fixed mechanical coupling to the crankshaft.
Electromechanical final controlling elements for charge cycle valves are known, for example, from German Patent DE 297 12 502 U1. The valves have a position of rest, which is located between a closed position and an open position and from which they can be deflected by electromagnets.
In order to open or close the valve, the winding of the respective electromagnet is energized, the necessary current being greater in a capture phase than in a holding phase in which the valve is held in an end position. Such an electromechanical method of activating a charge cycle valve has the advantage that in the case of a spark ignition internal combustion engine which intakes a mixture, the load control can be performed directly by driving the activating device for the inlet valves, at least in a wide load range. For example, for low loads it may be necessary to additionally activate a throttle valve.
It is thus known, for example from Published, Non-Prosecuted German Patent Application DE 196 10 468 A1, to implement the load control in the case of an internal combustion rail with gas valves which can be actuated freely. The load control is implemented by setting different opening and closing times of the charge cycle valves, and to assign a throttle valve which can be actuated appropriately to the charge cycle valves at high speeds and at simultaneously low engine torques.
Given a normal camshaft activation, the inlet valves are always opened and closed with full load times and a throttle valve is suitably set for load control in the intake tract.
As a result of the resolution of the fixed mechanical coupling between the valves and the crankshaft, which is obtained with the electromechanical activation, the control times of such valves can be freely selected so that the throttle valve no longer has to be activated, as a result of which throttle losses of the order of magnitude of 10 to 20% are eliminated.
Published, European Patent Application EP 0376714 A2 discloses a monitoring system which, when a fault is detected in electromagnetic pores which each activate an inlet valve, generates a fault signal in order to deactivate the respective inlet valves.
The actuation of the electromechanically activated valves as a function of the rotary position of the crankshaft and in accordance with predefined values of an operational control unit is generally carried out by a separate valve control unit which suitably sets or adjusts the energization of the electromagnets of the electromechanical final controlling elements. For this purpose, the valve control unit receives a signal relating to the crankshaft setting as well as suitable predefined values from the operational control unit of the internal combustion engine. For this reason, it is connected to the operational control unit via a communications line, generally via a CAN-BUS.
Although the communications lines have proven to be relatively operationally reliable, faults or failures of these connections are nevertheless possible. For example, a CAN-BUS can fail if a subscriber on the BUS does not understand a message and outputs a respective fault message and the latter then leads to avalanche-like fault messages from other BUS subscribers.
If the communications connection between the operational control unit and the valve control unit then fails, possibly even only for a brief time, the load of the internal combustion engine can no longer be controlled by the operational control unit.
It is accordingly an object of the invention to provide a circuit for load control and a method for an emergency operation of an internal combustion engine which overcomes the above-mentioned disadvantages of the prior art methods and devices of this general type, which takes in a mixture and has at least one electromechanically activated inlet valve and whose load control is brought about in the normal mode only by activating the inlet valves, with the result that load control is still possible in an emergency operating mode when the communications connection between the operational control unit and the valve control unit fails.
With the foregoing and other objects in view there is provided, in accordance with the invention, a method for implementing an emergency operation of an internal combustion engine having at least one electromechanically activated inlet valve. The method includes the steps of carrying out load control predominantly in a normal mode by the at least one electromechanically activated inlet valve being actuated by a valve control unit in accordance with values predefined by an operating control unit of the internal combustion engine. The operational control unit controls the throttle valve for changing a load. The valve control unit switches over an electromechanical activation of the at least one electromechanically activated inlet valve to permanently predefined control times if the operational control unit detects that the load control normally performed by actuating the at least one electromechanically activated inlet valve is not operating normally.
According to the inventive concept, the valve control unit of the internal combustion engine switches over the electromechanical activation of the inlet valves to permanently predefined control times (for example full-load times). The operational control unit moves a throttle valve, which is opened in the normal mode, into a suitable load setting if the communication or the exchange of data between the operational control unit and the valve control unit is disrupted. In the emergency operating mode, the internal combustion engine then behaves as an internal combustion engine with conventional camshaft valve drive.
Because it takes a certain amount of time to set the throttle valve to the necessary load setting, while it is possible to switch the electromechanical activation of the inlet valves over to the permanently predefined control times from one working cycle to the next, the valve control unit advantageously waits a specific time period before performing the switchover in order to ensure that the throttle valve has been moved into the necessary load setting. Either the initiation of the emergency operation can be indicated to the valve control unit by the operational control unit via a separate fault signal linexe2x80x94and of course the valve control unit can also signal a failure of the communications connection to the operational control unit via this fault signal linexe2x80x94or the valve control unit alone, or the valve control unit and operational control unit together, initiate the emergency operation independently.
In one optional embodiment, the valve control unit can also itself directly or indirectly actuate the throttle valve.
In accordance with an added mode of the invention, there is the step of using the operational control unit to start the emergency operation if communication between the operational control unit and the valve control unit is disrupted, by outputting a signal to the valve control unit via a fault line.
In accordance with another mode of the invention, there is the step of using the operational control unit and the valve control unit jointly and independently to start the emergency operation if communication between the operational control unit and the valve control unit is disrupted.
In accordance with a further mode of the invention, there is the step of using the valve control unit to switch over, with a time delay, to the permanently predefined control times in order to ensure that the throttle valve has been moved into a position which is suitable for the load control.
With the foregoing and other objects in view there is provided, in accordance with the invention, a circuit for load control of an internal combustion engine having at least one inlet valve that can be electromechanically activated. The circuit contains a valve control unit that receives and evaluates a crankshaft setting signal. The valve control unit exchanges data with an operational control unit of the internal combustion engine and activates the inlet valve in dependence on the crankshaft setting signal and on the data received from the operational control unit such that the internal combustion engine runs under a load requested by the operational control unit. In an event of a fault in an exchange of the data between the valve control unit and the operational control unit, the valve control unit switches over an activation of the inlet valve to permanently predefined control times and the operational control unit performs the load control by a throttle valve.
In accordance with an added feature of the invention, a bidirectional BUS connection is provided between the operational control unit and the valve control unit for exchanging the data. The valve control unit switches over independently to the permanently predefined control times in an event of a fault on the bidirectional BUS connection.
In accordance with an additional feature of the invention, a fault signal line is connected between the operational control unit and the valve control unit. The valve control unit switches over to the permanently predefined control times if a predetermined signal is present on the fault signal line.
In accordance with another feature of the invention, the valve control unit switches over, with a time delay, to the permanently predefined control times to ensure that the throttle valve has been moved into a setting that is suitable for the load control.
In accordance with a concomitant feature of the invention, the valve control unit has a way of intervening directly or indirectly in a control of the throttle valve, and when an emergency operation is initiated the valve control unit causes the throttle valve to be set to a necessary load setting.
Other features which are considered as characteristic for the invention are set forth in the appended claims.
Although the invention is illustrated and described herein as embodied in a circuit for load control and a method for the emergency operation of the internal combustion engine, it is nevertheless not intended to be limited to the details shown, since various modifications and structural changes may be made therein without departing from the spirit of the invention and within the scope and range of equivalents of the claims.
The construction and method of operation of the invention, however, together with additional objects and advantages thereof will be best understood from the following description of specific embodiments when read in connection with the accompanying drawings.